Apparatus for regulating brake control pressure

ABSTRACT

Apparatus for use with vehicle electro-pneumatic brake systems, said apparatus being characterized by a friction-free selflapping valve device responsive to opposing control forces reflecting the degree of electrical dynamic braking and the degree of fluid pressure controlling the pneumatic friction braking for automatically maintaining the called-for overall braking effect of the dynamic and friction braking combined, said valve device being operable responsively to variation of dynamic braking effort for automatically maintaining the called-for electro-pneumatic braking relationship by compensatingly varying the degree of delivery fluid pressure for the pneumatic braking system.

United States Patent 1 Balukin 3,724,912 Apr. 3, 1973 [54] APPARATUS FORREGULATING Primary Examiner-Duane A. Reger BRAKE CONTROL PRESSUREAttorney-Ralph W. Mclntire, Jr. et al.

[75] Inventor: Richard F. Balukin, Pittsburgh, Pa. ABSTRACT [73]Assignee: Westinghouse Air Brake Company,

wnmerding, Pa. Apparatus for use with vehicle electro-pneumatlc brakesystems, said apparatus being characterized by a Flledi J 1972friction-free self-lapping valve device responsive to [211 App]. No.:220,620 opposing control forces reflecting the degree of electricaldynamic braking and the degree of fluid pressure controlling thepneumatic friction braking for au- "303/16, 137/] tomaticallymaintaining the called-for overall braking a I I a a a a u [58] new ofSearch said valve device being operable responsively to varia- 137/1163627's tion of dynamic braking effort for automatically maintaining thecalled-for electro-pneumatic braking rela- [56] References Cltedtionship by compensatingly varying the degree of UNITED STATES pATENTSdelivery fluid pressure for the pneumatic braking s stem. 3,536,08910/1970 Sarbach ..303/52 X y 6 Claims, 1 Drawing Figure 37 1 3433 x[ i 2i E fi -45 9- H. as

lo- MA 2 2| I ?2 i 3 2o l 5 .7 .I I 47 \l ii TJfTLj/ H40 5 49 e t gAPPARATUS FOR REGULATING BRAKE CONTROL PRESSURE BACKGROUND OF THEINVENTION reduces accordingly as does the dynamic braking effect. Whenthe dynamic braking effect attains a certain low degree, a blendingvalve device provided in the system automatically actuates the pneumaticor fluid pressure portion of the system to automatically complement thefading dynamic braking with correspondingly increasing fluid pressurefriction braking which provides the primary braking effort during thelast stages of braking action.

Heretofore the blending or change-over function from dynamic to frictionbraking has been problematical in that the devices used for this purposehave not been sufficiently sensitive in responding to the electricalsignal from the wheel generator as such signal becomes increasinglyweaker. As a result of this inefficiency of the blending valve device,the braking action becomes somewhat erratic and inefficient during theblending period until the friction (pneumatic) braking takes overcompletely.

SUMMARY OF THE INVENTION The object of the present invention, therefore,is to provide a transducer device characterized by extreme sensitivityof response to electrical signals, including.

relatively weak signals, for converting said electrical signals topneumatic or fluid pressure signals either of directly proportional orof inversely proportional values.

The invention resides in an electro-pneumatic transducer or blendingvalve device capable of providing a continuous blending of dynamicbraking effort (compensating voltage) and friction braking effort(delivered pneumatic or fluid pressure) in a straight line relationship.The blending valve device comprises a three-way poppet type balancedcheck valve, a brushless direct current torque motor, a control bellowstype diaphragm, and a regulating bellows type diaphragm. Since both theregulating and control diaphragms have equivalent effective pressureareas, and the balanced check valve is held in lap position by a spring,build-up of delivery pressure follows that of control pressure. Deliverypressure is stabilized by its feedback on the regulating diaphragm, andis variable according to the prevailing force exerted by the torquemotor on the three-way valve or by variations of control pressure. Thebellows type diaphragms provide a valve structure with a minimum ofresistance and, therefore, a maximum of sensitivity responsive to smallchanges in electrical or pneumatic signals.

The single FIGURE drawing is an elevational view, primarily in section,of an electro-pneumatic transducer device embodying the invention.

DESCRIPTION AND'OPERATION' The drawing shows an electro-pneumatictransducer or blending valve device comprising a control valve portion 1and a brushless direct current torque motor 2.

The control valve portion 1 comprises a casing 3 provided with a supplyport 4, a delivery port 5, a control port 6, and an exhaust port 7.

A valve assembly 8 is housed within the casing 3 and comprises astationary mounting member 9 coaxially secured in said casing in astepped bore 10, with the lower end of said mounting member restingagainst a shoulder 11 formed adjacent the lower end of said steppedbore. A snap ring 12 cooperating with a groove 13 formed adjacent theupper end of stepped bore 10 serves to secure the mounting member 9 in afixed position in said stepped bore.

Valve assembly 8 further comprises a valve stem 14 extending coaxiallythrough mounting member 9. The valve stem 14 is guidably supported atopposite ends within guide bores 15 and 16 provided in transverse walls17 and 18formed adjacent the upper and lower ends, respectively, ofmounting member 9 for permitting limited reciprocable movement of saidvalve stem."

The lower end, as viewed in the drawing, of the stationarymountingmember 9 comprises a hollow cylindrical portion 19 fixed to andextending coaxially from the'upper portion of said mounting member withthe transverse wall 18 resting on shoulder 1 1 of casing 3.

A valve member 20 is supported by a pair of radially spaced-apartbellows type diaphragms 21 and 22 of different diameters andconcentrically disposed within the cylindrical portion 19, said valvemember being provided with an annular valve element 23 adapted forseating on an annular stationary rib type supply valve seat 24 formedwithin said cylindrical portion adjacent transverse wall 18. The outerperipheral portion of valve element 23 acts as a supply valve incooperation with supply valve seat 24 for controlling communicationbetween a fluid pressure supply chamber 25, connected to supply port4'via an opening 26 formed in the wall of cylindrical portion 19, and afluid pressure delivery chamber 27 connecting with delivery port 5 via apassageway 28 formed in said cylindrical portion.

An exhaust valve member 29 is concentrically and axially fixed on valvestem 14 within delivery chamber 27 and cooperates with the innerperipheral portion of valve element 23 acting as a valve seat forcontrolling communication between said delivery chamber and exhaust port7 via a fluted bore 30 formed in mounting member 9 and through whichsaid valve stem is reciprocably movable.

The upper end of valve stem 14, as viewed in the drawing, is anchored tothe mounting member 9 by an upper bellows type diaphragm 31 secured tosaid upper end of the valve stem and to the upper end of said mountingmember, while the lower end of said valve stem is similarly anchored tothe lower end of cylindrical portion 19 of said mounting member by alower bellows type diaphragm 32 of similar dimension as diaphragm 31,thus permitting axial movement of said valve stem in oppositedirections, said upper and lower diaphragms being identical instructure. A spring 33 encircling the upper diaphragm 31 is compressedsaid valve element, with the exhaust valve seated thereagainst, intoseating engagement with valve seat 24, such simultaneous disposition ofsaid exhaust valve and said valve element in their respective seatedpositions thus defining the lap position of the valve assembly. Itshould be evident that, in the absence of any fluid pressures acting onthe several diaphragms and of any other forces acting on valve stem 14,the biasing force of spring 33 must necessarily be slightly less thanthe combined oppositely acting forces of diaphragms 21 and 22 in orderto maintain the lapped condition of the valve assembly 8.

Valve member 20 has a passageway 35 extending axially therethrough,while mounting member 9 has a passageway 36 extending longitudinallytherethrough, said passageways being so disposed as to communicatedelivery chamber 27, via the annular space included between diaphragms21 and 22, with a feedback chamber 37 adjacent the upper end of saidmounting member and in which diaphragm 31 and spring 33 are disposed.

A passageway 38 communicates the inner volume of diaphragm 31 with anatmospheric chamber 39 open .to atmosphere via port 7, and a passageway40 connects the inner volume of diaphragm 32 with delivery chamber 27for reasons to be set forth hereinafter. The valve device 1 isconstructed such that the effective pressure area of exhaust valve 29over which fluid pressure in delivery chamber 27 is effective, isequivalent to the effective pressure area of diaphragm 32 over whichsuch delivery chamber pressure is effective, so that the opposingeffects on the two respective pressure areas are always in a balancedstate.

In considering the operation of ,the apparatus embodying the invention,operation of the valve portion 1 alone will be considered first, thenwill later be considered in conjunction with the torque motor 2. It willalso be assumed that there is no fluid pressure at delivery port 5 orcontrol port 6, but that supply fluid pressure is present at supply port4 and, therefore, in supply chamber 25 also. Since, in the lapcondition, valve element 23 is seated on supply valve seat 24, however,supply pressure from supply chamber 25 cannot flow to delivery chamber27.

If control pressure is established via control port 6 in a controlchamber 41 adjacent the lower end of valve stem 14 and diaphragm 32,such control pressure acting on the effective pressure area of saidlower end of said valve stem, is effective for disrupting the balancedor lapped condition of the valve assembly 8 and, therefore, causingupward movement of valve stem 14 to a pressure-increasing position inwhich valve element 23 is unseated from valve seat 24.

With valve element 23 in an unseated or supply position relative tovalve seat 24, in which it is shown in the drawing, pressurized fluidmay flow from supply chamber 25, past said unseated valve element, andthrough delivery chamber 27 to delivery port 5. At the same timepressurized fluid from supply chamber 25 also flows through passageways35 and 36 to feedback chamber 37 to act on the exposed area of the upperend of valve stem 14. When the force of fluid pressure in feedbackchamber 37 acting on the upper end of valve stem 14 equals the force ofsuch fluid pressure in control chamber 41 acting on the lower end of endof said valve stem, the valve stem is caused to move downwardly to aneutral position in which valve element 23 is restored to a seated orcut-off position relative to valve seat 24 for terminating further flowof pressurized fluid to delivery port 5. The relationship of diaphragm31 to diaphragm 32 and the relationship of diaphragms 21 and 22 tospring 33 are such that a 1:1 ratio is maintained betweenv controlpressure and supply pressure. Since exhaust valve 29,- during suchdownward movement of valve stem 14, remains in its closed position,valve assembly 8 assumes its lapped condition, above described, in whichthe forces acting on the several pressure areas are in a state ofequilibrium. For example, passageway 40 opens the inner pressure area ofdiaphragm 32 to delivery pressure in chamber 27 to balance the force ofsuch pressure acting upwardly on the lower side of exhaust valve 29 overan area equivalent to that area seated on valve element 23, while theunseated portion of said exhaust valve on the upper side thereof isexposed to atmosphere via fluted bore 30 and exhaust chamber 39, as isthe inner pressure area of diaphragm 31 via passageway 38. The degree ofincrease in delivered pressure is determined by the degree of controlpressure established in control chamber 41 on a 1:1 ratio, as abovenoted.

It should be evident to one skilled in the art that a decrease ofestablished pressure in control chamber 41 again disrupts the state ofbalance of the valve assembly 8 in that pressure acting in feedbackchamber 37 becomes effective for causing downward movement of valve stem14 to a pressure-reducing position in which exhaust valve 29 is operatedto an unseated or exhaust position relative to valve element 23. Fluidpressure in delivery chamber 27 and delivery port 5 is exhausted toatmosphere past the unseated exhaust valve 29, via fluted bore 30,exhaust chamber 39 and exhaust port 7. The degree of reduction ofdelivered pressure in delivery chamber 27 and delivery port 5 isgoverned by the degree of reduction of control pressure in controlchamber 41, and upon attainment of such degree of reduction, the valveassembly 8 once more assumes its lap condition.

By employing the bellows type diaphragms 21, 22, 31, and 32 in the valveassembly 8, friction in the valve assembly is held to a minimum, thusimparting a high degree of sensitivity to the valve structure andproviding a valve device operatively responsive to the slightest changein the forces acting on valve stem 14. This characteristic makes thevalve device 1 highly suitable for use as a blending valve in anelectro-pneumatic brake system above described.

The valve portion 1 and torque motor 2 are cooperatively secured to eachother so that an eccentric cam member 42 formed on a sleeve member 43secured coaxially to a torque output shaft 44 of said torque motor by aset screw 45 projects axially into a bearing axial movement of valvestem 14. Because of the particular structure of the valve portion 1,that is, the use of bellows type diaphragms 21,22, 31, and 32 and ofdisc type valve members 20 and 29, the necessary flow capacity of fluidpressure between the several ports,

- passageways and chambers can be provided with only a minimum of axialmovement of valve stem 14. Hence, rotation of the torque motor shaft 44can be limited to -a maximum angular displacement of i a range withinwhich the relationship of the force of the torque motor 2 transmitted tothe valve stem 14 remains essentially linear.

Since, as above noted, the valve stem 14 must be restored to its neutralaxial position in order to restore valve assembly 8 to its lapcondition, it is necessary that eccentric 42 be connected to torquemotor 2 by yieldable resilient means (not shown) to permit forceablereturn of said eccentric to its normal angular position, notwithstandingcontinued current input, so that said valve stem and said valve assemblymay resume their neutral and lap positions, respectively.

With the type of valve structure, as herein described, characterized bya high degree of sensitivity, it should be evident that, with the valveassembly 8 in its lapped condition, a slight change or disturbance ofthe balanced forces acting on valve stem 14, such as a reduction orincrease of control pressure in chamber 41, will cause movement of saidvalve stem accordingly, as above described, to effect a correspondingchange of fluid pressure delivered to delivery port 5. Similarly, anyaxial force exerted on the valve stem 14 by the eccentric 42 of torquemotor 2, also effects a corresponding adjustement of fluid pressure atdelivery port 5 until the balance of forces is restored and valveassembly 8 is returned to the lap position.

When valve device 1 is used with torque motor 2 as a blending valve inan electro-pneumatic brake system, a brake application initiated by theoperator effects actuation of dynamic braking to establish a preselectedmaximum current at the torque motor while simultaneously causing thecontrol chamber 41 to be charged with control fluid at a preselectedmaximum pressure. Control pressure in chamber 41 exerts an upwardlydirected force on valve stem 14, while the torque motor 2 is arrangedsuch that torque motor current exerts a downwardly directed force onsaid valve stem, the maximum current and maximum control pressure beingso selected as to produce respective oppositely directed equal forcesacting on said valve stem to initially establish a lap condition of thevalve assembly 8. With retardation of the vehicle, due to the effect ofdynamic braking, and consequent reduction of current at the torque motor2, the downward force thereof acting on valve stem 14 is accordinglyreduced, thereby rendering control pressure in control chamber 41effective for moving said valve stem upwardly to cause unseating ofvalve element 23 off supply seat 24. As a result, supply pressure fromport 4, in the manner above described, may flow to delivery port 5 andto feedback chamber 37 until the balance of forces and lap condition ofvalve assembly 8 are restored.

Obviously, a subsequent increase of torque motor current would causedownward movement of valve stem 14 and consequent unseating of exhaustvalve 29 to effect venting and reduction of delivery pressure at port 5until a balanced state of forces and lap condition of the valve assembly8 are once more restored, as above described. o i

It should thus be seen that as dynamic braking effect decreases, thevalve portion 1 and torque motor 2 operate cooperatively. for effectinga compensating increase in pneumatic braking effect, or conversely ifdynamic braking effect is increased, pneumatic braking iscorrespondingly decreased, the result being a smooth blending of dynamicand pneumatic braking actions in maintaining the desired overall brakingcalled for.

In order to provide an inshot delivery pressure, which assures immediateresponse of pneumatic braking to a reduction in dynamic braking, theseveral pressure areas and compression rating of spring 33 of valveportion 1 maybe designed and selected such that the maximum torque forceof shaft 44 corresponding to maximum dynamic braking is able to effect areduction of all but a predetermined degree of delivery pressure at port5 corresponding to a preselected input pressure desired. This limitationof maximum torque output by the torque motor 2 can be accomplishedelectrically by limiting the maximum voltage of the torque motor, ormechanically by adjusting the lever arm (not shown) controlling theamount of angular displacement of shaft 44 and hence thestroke ofeccentric 42. Thus, with maximum dynamic braking effort, a preselecteddelivery pressure at port 5, such as 10 psi., for example, can beprovided. As dynamic braking fades, delivery pressure is increased at arate inversely proportional to the rate of decrease of torque motorcurrent, thus maintaining a constant retarding force due to the combinedblending of the dynamic and pneumatic braking effects. When dynamicbraking has terminated, delivery pressure at port 5 is proportionalsolely to control pressure at control port 6 established by the operatorin accordance with desired retardation.

If desired, the valve portion 1 may be arranged with torque motor 2 toprovide an electric-to-pneumatic transducer by eliminating controlpressure at control chamber 41 and reversing the direction of torquemotor force acting on valve stem 14.

If desired, if the valve portion 1 is used solely as a pneumaticallyoperable valve device without the torque motor 2, a one-way check valvedevice 47- may be arranged, as shown, between a pair of conduits 48 and49 connected to delivery port 5 and control port 6, I

respectively, with the direction of'flow through said check valve deviceas shown by the arrow, to provide a more direct and rapid release ofdelivery pressure from port 5 via conduit 49, the conduit via whichcontrol pressure is dissipated when reduced by the operator. Thisarrangement provides a quicker response to reduction of control pressurein chamber 41.

Having now described the invention, what I claim as new and desire tosecure by Letters Patent, is:

1. Fluid pressure control apparatus for use in an electro-fluid pressurecontrol system, said apparatus comprising the combination of:

a. a casing having a fluid pressure supply port, a fluid pressuredelivery port, a fluid pressure control port, and an exhaust port;

nications between the several ports, 10

c. said valve stem being operable in response to control fluid pressureat a preselected degree provided via the control port and acting on theeffective pressure area of the bellows diaphragm at one end of the valvestem, to a first position for operating said valve means to a supplyposition in which said supply port is communicated with said deliveryport for effecting delivery of fluid pressure at a degree correspondingto said preselected degree;

d. passage means communicating said delivery port with the effectivepressure area of the bellows diaphragm at the end of said valve stemopposite said one end, said valve stem being restorable to its saidneutral position in response to equalization of pressure forces actingon opposite ends thereof and being operable in response to a preselectedreduction of control pressure acting on said one end of the valve stem,to a second position for operating said valve means to an exhaustposition in which said delivery port is communicated with said exhaustport for effecting a corresponding reduction of fluid pressure at thedelivery port and at'said' opposite end of the valve stem and consequentrestoration thereof to its said neutral position; and

e. means for exerting a yieldable and variable axially directedcomplementary force on said valve stem independently of said controlpressure and acting in conjunction therewith for effecting an increaseor decrease in the degree of fluid pressure at the delivery portaccording to the combined effects of said control pressure and saidcomplementary I force.

2. Fluid pressure control apparatus, as set forth in claim 1, whereinsaid bellows diaphragms at the opposite ends of saidvalve stem arecharacterized by equal effective pressure areas and equal resiliencyratings.

3. Fluid pressure control apparatus, as set forth in claim 1, whereinthe last said meanscomprises an electrical torque motor for exertingsaid axially directed force at a degree corresponding to an electricalinput impressed thereon.

4. Fluid pressure control apparatus, as set forth in claim 3, whereinthe last said means further comprises eccentric means operativelyconnecting the torque motor to said valve stem and being yieldablyangularly displaceable out of a normal angular position for transmittingtorque motor force to said valve stem and ef-' fecting axial movement ofsaid valve stem.

5. Fluid pressure control apparatus, as set forth in claim 4, whereinangular displacement of said eccentric means is limited to a rangewithin which the relationship of the torque motor force transmitted tothe valve stem remains essentially linear.

6. Fluid pressure control apparatus, as set forth in

1. Fluid pressure control apparatus for use in an electro-fluid pressure control system, said apparatus comprising the combination of: a. a casing having a fluid pressure supply port, a fluid pressure delivery port, a fluid pressure control port, and an exhaust port; b. a self-lapping valve assembly operatively disposed in said casing and including: i. an axially movable valve stem, ii. valve means carried by said valve stem, iii. respective bellows type diaphragms disposed at opposite ends of said valve stem and acting in opposing relation for biasing the valve stem to a neutral position in which said valve means occupies a lap position for closing all communications between the several ports, c. said valve stem being operable in response to control fluid pressure at a preselected degree provided via the control port and acting on the effective pressure area of the bellows diaphragm at one end of the valve stem, to a first position for operating said valve means to a supply position in which said supply port is communicated with said delivery port for effecting delivery of fluid pressure at a degree corresponding to said preselected degree; d. passage means communicating said delivery port with the effective pressure area of the bellows diaphragm at the end of said valve stem opposite said one end, said valve stem being restorable to its said neutral position in response to equalization of pressure forces acting on opposite ends thereof and being operable in response to a preselected reduction of control pressure acting on said one end of the valve stem, to a second position for operating said valve means to an exhaust position in which said delivery port is communicated with said exhaust port for effecting a corresponding reduction of fluid pressure at the delivery port and at said opposite end of the valve stem and consequent restoration thereof to its said neutral position; and e. means for exerting a yieldable and variable axially directed complementary force on said valve stem independently of said control pressure and acting in conjunction therewith for effecting an increase or decrease in the degree of fluid pressure at the delivery port according to the combined effects of said control pressure and said complementary force.
 2. Fluid pressure control apparatus, as set forth in claim 1, wherein said bellows diaphragms at the opposite ends of said valve stem are characterized by equal effective pressure areas and equal resiliency ratings.
 3. Fluid pressure control apparatus, as set forth in claim 1, wherein the last said means comprises an electrical torque motor for exerting said axially directed force at a degree corresponding to an electrical input impressed thereon.
 4. Fluid pressure control apparatus, as set forth in claim 3, wherein the last said means further comprises eccentric means operatively connecting the torque motor to said valve stem and being yieldably angularly displaceable out of a normal angular position for transmitting torque motor force to said valve stem and effecting axial movement of said valve stem.
 5. Fluid pressure control apparatus, as set forth in claim 4, wherein angular displacement of said eccentric means is limited to a range within which the relationship of the torque motor force transmitted to the valve stem remains essentially linear.
 6. Fluid pressure control apparatus, as set forth in claim 5, wherein said angular displacement of said eccentric means is limited to + or - 15*. 